A purple flag at the beach is not decoration, but a warning that something unusual is present in the water that swimmers should be aware of before going in.

Unlike red or yellow flags that focus on waves and currents, the purple flag specifically signals the possible presence of dangerous or irritating marine life near the shoreline. It may include jellyfish, stingrays, or other sea creatures that can cause painful stings if accidentally touched while swimming or walking in shallow water.
Swimming is often still allowed when a purple flag is flying, but lifeguards recommend extra caution and awareness of where you step and swim.